movable stalks to allow sight in different directions, ability to emit chemical

cues to identify one another and signal mating, and can even change color to match their habitat.

✪ Dissection (Observations and Comparing) ✪

✪ Integumentary System ✪

The bodies of arthropods are covered by an exoskeleton, or cuticle, that contains chitin. This makes up the integumentary system. The tough outer covering, against which muscles work, is secreted by the epidermis fused with it. The exoskeleton remains fairly flexible at specific points, allowing the exoskeleton to bend and appendages to move. The exoskeleton protects arthropods from water loss and helps to protect them from parasites, predators, and harm.

The exoskeleton does not go through growth, but molts. For a crayfish to grow, it must shed its exoskeleton and then re-grow a new and larger one. When a crayfish moults it is very vulnerable to both injury and predation so, they must spend the two or three days it takes to re-grow its exoskeleton relatively inactive in its refugia. Young crayfish molt 6 to 10 times during their first year while older crayfish moult 3 to 5 times during their second (and, typically, final) year of life.